Newer drug combinations for malaria

When is confirmed malaria diagnosis cost-effective?

Barnish, Bates, and Iboro recently highlighted the need for improved
malaria diagnostics and called for economic evaluation to determine the
best approach to using them alongside treatment with artemisinin-based
combination therapies (ACTs)[1]. We have developed mathematical models
that address these questions in a range of transmission settings, building
on published work on the cost-effectiveness of ACTs[2].

The factors determining cost-effectiveness include the prevalence and
types of malaria, the cost of tests relative to subsequent treatment costs
for patients diagnosed “positive” and “negative”, the community or health
care setting [3,4] and long-term impact on drug resistance[2].

In low transmission settings, where most fevers are not caused by
malaria and asymptomatic parasitemia is uncommon, using precious ACTs
without accurate diagnosis is wasteful. Current research by Morel et al.
suggests that rapid diagnostic tests (RDTs) are likely to be cost-
effective where slide positivity is quite low (assuming RDTs cost US$0.55
-$1.10 and ACTs cost US$1.50 – 2.88)[5]. Where non-falciparum malaria is
common, more expensive RDTs which can differentiate parasite species
should be considered.

High transmission settings are more complex. Although it is rarely
used, good quality microscopy should be cost-effective where malaria is
frequently diagnosed. Microscopy may be preferable to RDTs because it
allows parasitemia to be quantified, and RDTs detect very low levels of
parasitaemia which may not be clinically significant in high transmission
areas. Better information is needed on the fate of those diagnosed
“malaria negative”.

We are currently refining the models for economic evaluation of ACTs
to take into account a wider range of diagnostic options, the implications
of imperfect implementation of ACTs, and the impact on drug resistance.
ACTs are an order of magnitude more costly than chloroquine or SP
monotherapy and issues of targeting and diagnostics are critical. However,
the choice of treatment protocol must be evidence based, taking into
account the costs and consequences of accurate and inaccurate diagnosis
and the continued use of ineffective drugs.